This invention relates in general to semiconductor integrated circuits, and more particularly to power integrated circuits which are serially connected between a power source and a load, having both logic and power switching transistors on the same chip.
A common application for power switching devices is as series switching elements connected between a power supply and a load. It is now possible to integrate logic circuitry on the same chip as the power switching device in such an application. In this application, the power supply voltage for the logic devices is the same as the substrate voltage of the power device. Logic circuitry is usually formed in a section of the chip which is electrically isolated from the power transistor, thus preventing the power supply voltage from contacting the logic devices.
In the past, integrated circuits with both logic and power switching transistors (power integrated circuits) provided the power supply voltage for the logic transistors by bonding a wire from a supply lead, which extends from the package, to a supply bond pad on the chip surface. The wirebond area available on the power supply lead is usually small because the lead must attach to the die mount portion of the package. The small area results in a more difficult and less reliable wirebond. The supply bond pad, required a significant amount of chip surface area which increased the size and cost of the chip. Several metal interconnections were formed on the chip surface to connect the supply pad to the various devices in the logic section powered by the supply voltage. The metal interconnections complicated the design of other interconnections made on the chip surface. A minimum number of metal interconnections on the chip surface is desirable.
Accordingly, it is an object of the present invention to provide an improved semiconductor integrated circuit with both power switching transistors and logic transistors on the same chip which does not require a power supply bond pad or power supply bond wire.
It is a further object of the present invention to provide a power integrated circuit which is less expensive to manufacture than current methods.
It is a further object of the present invention to provide a power integrated circuit with improved reliability.
It is a further object of the present invention to provide a power integrated circuit which requires a minimum number of metal interconnections on the chip surface to conduct power supply current to the logic section of the integrated circuit.